The invention relates to an open end friction apparatus of the type having two friction rollers driven in the same rotational direction and arranged adjacent one another to form a yarn spinning wedge slot. Fiber material in the form of single fibers is fed by means of a fiber feed channel to the wedge slot where it is twisted together in a yarn formation region of the wedge slot to form a yarn that is withdrawn by a withdrawal device. The mouth of the fiber feed channel, which is inclined to the withdrawal direction of the yarn, is disposed in the region of the yarn formation region of the wedge slot.
With a known apparatus or device of the above mentioned kind, described in published European patent application No. (EP-OS) 62 404, an opening or fiber inlet chamber connected at the fiber feed channel is disposed in the region of the wedge slot closesly adjacent to the yarn building region and extending approximately over the entire length of the wedge slot. A suction device is additionally connected to the opening chamber for applying a suction air flow effect against the yarn withdrawal direction. The lateral walls of the opening chamber are provided with concave surfaces which conform to the cover surfaces of the two rollers and which are disposed at a small distance from these cover surfaces so that the least possible air can penetrate in this region. The actual opening of the opening or inlet chamber is arranged at the wedge slot and exhibits a slight component toward the cover surface of the roller rotating inwardly toward the yarn formation region. The roller rotating in toward the yarn formation region is constructed as a so-called suction roller which exhibits a perforated cover surface and an inside suction insert, which suction insert is fitted with a slit opening at the yarn formation region. The roller rotating outwardly from the yarn formation region possesses a cylindrical closed cover surface.
In this kind of device, the fibers are twisted together to form a yarn on the basis of the connection through friction at the cover surfaces, which yarn is then withdrawn in the longitudinal direction of the wedge slot. There exists the danger that single or also several fibers are carried from the roller rotating outwardly from the yarn formation region and are lost as far as yarn spinning is concerned or also form a fiber collection reverting again to the yarn formation region which leads to non-uniformity in the yarn.
In another apparatus, described in German published unexamined application (DE-OS) No. 3213478, which is principally used for the manufacture of so-called wrapped yarn that consists of a previously finished yarn and fibers wrapped there around, there are likewise two adjacently arranged rollers driven in a similar rotational direction. The two rollers form a wedge slot in which single fibers are guided between two guide surfaces toward the direction of the wedge slot, which, if necessary, should be formed with facing walls into a channel. These guide surfaces end at a relatively large distance from the wedge slot. In order to provide that the fed fibers do not extend near to the cover surfaces of the two rollers, auxiliary air stream suction which should have an increased stream speed is provided laterally of the two guide surfaces. Such an arrangement does not seriously hinder the carrying of fibers with the roller rotating outwardly of the yarn formation region. It is therefore provided that the rollers are surrounded with a guide surface which should form a guide channel in which fibers that were eventually carried along with the roller are guided around this roller and again fed to the wedge slot.
The invention is based upon the problem to so construct an open end friction spinning arrangement of the above mentioned kind that it is assured with a high degree of certainty that fibers are not carried with the roller rotating outwardly from the yarn formation region.
This problem is thereby solved by the invention providing an air inlet opening between the mouth of the fiber feed channel and the yarn formation region at the side of the roller rotating outwardly from the yarn formation region and using the air inlet opening to create an air stream directed from the cover surface of this roller to the yarn formation region.
The air stream facilitated by the air inlet opening means provides that the fibers which eventually are carried with the roller rotating outwardly from the yarn formation region are loosened therefrom and remain in the yarn formation region, in which they are bound into the yarn. It is thereby possible to spin a very uniform yarn because a constant volume of fibers in the yarn formation region is guaranteed.
In an advantageous embodiment of the invention it is provided that the cover surface of the two rollers, at least at the side of the mouth of the fiber feed channel, are covered by means of a plate with shell shaped recesses conforming to the countour of the rollers. An inlet channel with a slit formed mouth is arranged in the plate adjacent the mouth of the fiber feed channel at the cover surface of the roller turning outwardly from the yarn formation region. The thereby facilitated air stream can be effected through a suction which also creates the transport air stream in the fiber feed channel. Through the selection of the cross section of the air inlet channel, which cross section can be formed to be adjustable, as necessary, the effect of the air stream can be controlled.
In further arrangements of the invention it is provided that the air inlet channel is connected at an air pressure source. In this arrangement the effect of the auxiliary air stream can be controlled by adjusting the pressure. With this arrangement it can advantageously be further provided that between the air inlet channel and the fiber feed channel there are arranged one or several connecting channels having components in the transport direction of the fibers. Thereby it is possible with the help of the air pressure source on the basis of an injector principle to create the transport air stream in the fiber feed channel or at least to support the same.
In another arrangement of the invention it is provided that the roller rotating outwardly from the yarn formation region exhibits a perforated cover surface and an air pressure insert fitted with a slit opening at the region between the mouth of the fiber feed channel and the yarn formation region. With this air pressure insert an air stream is created which assures the loosening of fibers that may be carried at the cover surface of the roller rotating outwardly from the yarn formation region and the loosened fibers are returned to the yarn formation region.
In further arrangements of the invention it is provided that the air inlet opening extends along a cover surface or line approximately over the entire length of the roller rotating outwardly from the yarn formation region. With this arrangement it is achieved that the yarn being formed is held securely in the wedge slot downstream of the mouth of the fiber feed channel so that the yarn achieves a uniform rotation/twisting. Irregularities in the yarn are also precluded in this manner. Through the air inlet opening, which offers the only possibility for air entry in this region of the wedge slot, an air stream with a certain alignment is achieved while only a relatively small air volume is necessary therefore.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.